In this exercise we will plot 40 theoretical earthquake events at the juncture of two tectonic plates.Â Students will then analyze the pattern of earthquake locations and compare these patterns to possible plate boundaries.

Learning Objectives

Student will learn to recognize the earthquake patterns associated with plate tectonic boundaries.

Step One

Plot the Earthquake Data found in Table #1 onto the Area Map (Figure #1). Feel free to duplicate this map to use as work copies. Place a dot or small circle on the map to represent each earthquake event (epicenter). Next to your earthquake location write the value of the depth at which that earthquake occurred (focus).

Step Two

Using the East-West Crossection (Figure #2) plot the surface location (epicenter) of each earthquake and then, based on the depth related to each earthquake event, plot the earthquake focus. On the crossection trace the top and bottom of the plate based on the earthquake focus depths.

Step Three

Answer the following questions.

Question #1: Does the pattern of deep and intermediate earthquakes indicate a tectonic plate boundary? If so, describe.

Question #2:Â Is it possible to predict the thickness of this plate? How thick could this plate be? Does this thickness relate to a continental plate or oceanic plate? Oceanic plates are not 100 kilometers thick, discuss what then could account for the apparent thickness of this descending plate?

Question #3:Â Can a second pattern be found that could be describing the other plate? Describe.